An image forming device is provided with a thermal fixing unit and a U-shaped sheet guide. The thermal fixing unit includes a heat roller and a pressure roller nipping a sheet therebetween for thermally and pressurizingly fixing a toner image onto the sheet. Here, toner is a developing agent. The sheet guide is adapted to guide the sheet discharged from the thermal fixing unit to a sheet discharge opening positioned higher than the thermal fixing unit so as to turn around the sheet.
Conventionally, the sheet heated at and discharged out of the fixing unit may be curled in a sleeve like or a rainwater guttering fashion whose axial direction is coincident with a sheet feeding direction. One example to avoid such sheet curl is disclosed in Japanese Patent Application Publication No. 2001-48399.